I have often thought of electrical devices to achieve the same end. A small motor turning a cam to activate the trigger for instance or a solenoid activated trigger in series with a NO switch which is closed by the bolt returning to battery would fulfill the one shot per trigger pull requirement but I expect the ATF would disagree. If you think about it a Gatling gun (Mini gun) is technically not a machine gun since it is not self activated by recoil or expanding propellant gas. It just sits there until someone turns the crank. Add an electric motor and you can rip off four thousand rounds per minute and I would fully expect the ATF to consider it Class-III along with any other electrical add on mechanism.
As I said, too bad, so sad!
Regards,
GtG
This is actually a story about a poor business strategy for the product. The guy clearly knew that he was producing a product for a market which is already highly regulated and controversial. His strategy should have been focused on quick sales of the product full well knowing that the political climate could change at anytime and kill off the market window for the product.